As part of the deal, Rentrak will acquire the U.S. TV measurement business of WPP's Kantar Media. In exchange, WPP will receive $98 million of Rentrak stock. The ad holding company will also buy another $56 million of shares directly from Rentrak. WPP can acquire additional Rentrak shares on the open market so long as its total stake doesn't exceed 20%.

The news sent Rentrak's shares up 11% to $71.89 in recent trading.

Rentrak appeals to marketers, because of its ability to tie viewership to consumer buying behavior. The company has agreements with cable and satellite providers to collect data from set-top boxes, which it then matches with other data sets on consumer purchases. Rentrak measures viewing from more than 29 million televisions in 210 local markets and said it is working with the Media Rating Council to receive accreditation.

By linking up with Kantar Media, Rentrak will be able to integrate its products with Kantar Media's U.S. digital media, advertising expenditure and purchase data services. Kantar Media's non-U.S. businesses aren't impacted by this deal.

That kind of granular data from Rentrak will be helpful for WPP's unit GroupM, which will use Rentrak's national and local TV measurement for media planning and buying in the U.S. GroupM, the parent of agencies such as Mindshare and MEC, says it represents about a quarter of the U.S. TV market, citing data from research firm RECMA.

“We see a TV marketplace that continues to fragment and we see that our ability to drive our clients’ business requires more and more granular data beyond just sex and age and geography," said Rino Scanzoni, GroupM’s chief investment officer. "The immediate value for us is really getting a robust database from set top box viewing which we can then marry with additional data for much more precise targeting for clients."

While GroupM will use Rentrak data for refined targeting purposes, it will continue to use Nielsen data for trading purposes, Mr. Scanzoni said.

The WPP agreements come as Rentrak has been aiming to get a bigger slice of the audience measurement business, which has long been dominated by Nielsen. Rentrak has struck a series of deals with broadcasters whose executives often complain that Nielsen's sample-based survey understates their audience, though typically when they hire Rentrak they also continue to work with Nielsen.

Nielsen provides the ratings currency upon which national TV advertising is bought and sold, based on a sampling of viewing activity of approximately 22,000 U.S. homes. Nielsen uses U.S. census data to make sure its sample is reflective of the market population.

Nielsen also has marketing performance analytics capabilities. The company has a joint venture called Nielsen Catalina Solutions that uses big data to link the marketing campaigns that consumers see with the products that they buy from consumer packaged goods companies.

"Nielsen is focused on measuring video however consumers access it and we are well positioned to continue providing market trusted independent measurement services to the industry," Nielsen said. " Our accredited census-based methodology remains the gold standard for television audience measurement and we continue to collaborate with our clients and industry organizations to ensure the solutions we deliver reflect the realities of the market and serve the needs of the industry.”